Method for producing an adhesive closing element$I()

ABSTRACT

The invention relates to a process for producing an adhesive closing element comprising a plurality of hook elements connected to a backing ( 10 ) forming a single piece therewith and being disposed symmetrically thereon. Said elements are provided in the form of a stem component ( 17 ) having a head piece ( 16 ), wherein a deformable material is introduced into a forming zone in between a production master ( 3 ) and a forming tool ( 5 ). The opposite-lying defining walls, at least when seen in a longitudinal section of the respective forming cavity ( 12 ) are provided with a continuous convex trajectory, whereby a continuous transition between the cross-sectional forms of the stem component ( 17 ) and the head piece ( 16 ) is provided for a hooking means of the backing ( 10 ) resulting in seamless removal.

[0001] The invention relates to a process for producing an adhesive closing part with a plurality of interlocking means which have a symmetrical structure and which are connected integrally to a backing, in the form of a stem part which is provided with a head part and in which a moldable material is supplied to the shaping zone between a pressure tool and a molding tool and they are driven such that the backing is formed in the shaping zone and conveyed in the transport direction, and in which mold cavities with boundary walls opposite one another are used as the shaping element on the molding tool.

[0002] WO 00/00053 A1 discloses a generic process for producing an adhesive closing part with a plurality of interlocking means which are formed integrally with a backing, in the form of stems which have end-side thickened areas, in which a moldable plastic material in the plastic or liquid state is supplied to the gap between a pressure roller and a mold roller and they are driven such that the backing is formed in the gap as the shaping zone and is conveyed in the transport direction in which the shaping element on the molding tool is a screen which has continuous cavities and in which the interlocking means are formed by the moldable material at least partially setting in the cavities of the screen.

[0003] On the inside of the first shaping screen, the second shaping element is an inner, second screen. Here the size of the cross section of the openings of the inner second screen is chosen to be somewhat greater than the cross sectional size of the cavities of the first screen, so that when the plastic is added, end-side thickened areas of the stem are formed. The stem cross sections which are produced in doing so are generally rotationally symmetrical and the stems themselves form cylindrical elements which run with their base part into the backing material and are provided on their free end with a head part which is formed by the second screen with its shaping cavities. As a result of the different cross sectional sizes between the mold cavities of the first screen for the stem parts and the mold cavities of the second screen for the head parts, there are an edge-like transition between the indicated parts and associated high adhesive forces of at least the head part within the mold cavities of the second screen, with the result that, when the backing with the interlocking means is removed from the mold, these high adhesive forces which can lead at least in part even to tearing off of the molded head part when the process sequence is not adjusted precisely must be overcome. Since head parts which are produced with the described process are also made essentially cylindrical and/or provided with corner end segments, the head parts, in the same way as the stem parts, are made relative rigid and less pliable; this leads to difficulties if for example the head parts of the same type are to fit into the respective intermediate spaces of the interlocking means of another closing part, which spaces have been left open, to produce a complete closure and these intermediate spaces are not cleared first of all as desired for the interlocking due to the rigidity of the interlocking means.

[0004] The interlocking means produced using the above-described process have, as already shown, rotationally-symmetrical stem cross sections, the stems themselves first forming cylindrical elements. If these stems are then subjected to a calendering process, in which a calender roller presses on the closure material against the action of a counterstay roller, the free stem ends are widened in cross section on their head side; this supports the desired head shaping for the respective interlocking means and the stems themselves assume concave paths in cross section, as is disclosed in WO 99/60880 A1. Only the concave path in this connection is produced by a separate calender production process and not by means of the screen production process according to WO 00/00053 A1 with the known mold removal problems.

[0005] Proceeding from this prior art, the object of the invention is to further improve the known process such that good ejection of the interlocking means after the shaping process is achieved, even at very high production rates, and that the interlocking means produced in this way leads to closing parts which adhere well and which can be joined to one another. This object is achieved by a process with the features of claim 1.

[0006] Because according to the characterizing part of claim 1, viewed at least in the lengthwise section of the respective mold cavity the opposing boundary walls are provided continuously with a convex path, a continuously running transition is achieved between the cross sectional shapes of the stem part and the head part for the interlocking means of the backing. This continuous transition along the convex path then leads essentially to unimpeded mold removal process without the danger of the head parts tearing off from their assigned stem part over sharp-edged shape transitions. Moreover, head parts can be formed with a height which decreases toward their outer peripheral edge such that a type of interlocking lip is formed, with the consequence that the head parts are elastically very flexible on the edge side and easy interlocking among one another or with an assigned loop material is achieved. With the pertinent fitting of interlocking means of one type into the intermediate spaces of the interlocking means of another or same type the lips of the head parts are pushed elastically aside, to immediately re-assume their original position after engaging and to block the initially cleared intermediate space again. In this way very favorable closing behavior between the two adhesive closing parts which form a closure is possible.

[0007] In one preferred embodiment of the process as claimed in the invention, the curvature of the respective path in the direction of the head part which is to be molded is made more pronounced than in the direction of the base part via which the stem part is connected to the backing. This curvature has proven especially favorable both for removal from the mold and also for producing the desired geometries of the interlocking means. Preferably it is provided here that, viewed from the lengthwise direction of the stem part in the direction of the head part, the respective path with its more pronounced curvature begins above the middle, preferably in the upper third.

[0008] In one especially preferred embodiment of the process as claimed in the invention, some of the lengthwise sections with their convex path run into the corners of the boundary walls such that the cross section of the stem part and/or of the head part is formed as a polygon, especially a hexagon. Although as a result of the convex paths it would be possible to make the interlocking means rotationally symmetrical, it has proven advantageous to provide a hexagon or other polygonal shape for them. As a result of this edge configuration, especially in the area of the head part, major deviations occur on the outer peripheral area; this makes it easier for the interlocking means, also in the form of a coating of another closing part which forms a closure with the initially mentioned closing part, to accomplish effective interlocking. The indicated hexagonal or polygonal shape makes it possible to clearly increase especially the peeling strength of the closure.

[0009] In another preferred embodiment of the process as claimed in the invention, the respective mold cavity is made as part of a mold screen or mold grating of the molding tool. In this way it is possible to produce the entire structure of the interlocking means with only one type of screen or grating.

[0010] But in a process of a different nature it can also be provided that each part of the interlocking means, preferably both the head part and also the stem part, has its own mold screen or mold grating with different cross sections. In this way a plurality of configuration possibilities can be achieved in the production of the interlocking means.

[0011] Since the mold cavities to be produced have a complex structure, in continuation of the process as claimed in the invention it has proven especially advantageous to produce them with their paths by way of a galvanic coating process or by means of a laser.

[0012] In another preferred embodiment of the process as claimed in the invention, the mold screen or the mold grating is made as a jacket part which is placed around the shaping tool in the form of a roll body and is joined to it. Thus, if necessary the mold screen or the mold grating can be easily replaced as a closing part and the roller-like shaping tool is inherently preserved for the continuing production process.

[0013] With the process as claimed in the invention interlocking means can be produced which have a geometrically very small structure so that implementation of micro-adhesive closures is easily possible. Furthermore, the density of the interlocking means per cm² of backing material can be very dramatically increased, and as a result the adhesive force between the adhesive closing parts of a closure. Here it has proven especially advantageous to make the mold cavities and moreover the interlocking means as rotationally symmetrical parts, especially in the form of hyperboloids.

[0014] The process as claimed in the invention is detailed below using one embodiment. The figures are schematic and not to scale.

[0015]FIG. 1 shows a side view of a device for implementing the process as claimed in the invention, a view which is highly schematically simplified and partially cutaway;

[0016]FIG. 2 shows a lengthwise section through one mold cavity as shown in FIG. 1, greatly enlarged;

[0017]FIG. 3 shows an interlocking means as can be produced using the mold cavity shown in FIG. 2;

[0018]FIG. 4 shows an overhead view of the backing strip material produced with the device as shown in FIG. 1 with several interlocking means as shown in FIG. 3.

[0019]FIG. 1 schematically shows parts of a device for implementing the process as claimed in the invention with an extruder head 1 as the feed means for a plastic which is in the plastic or liquid state, especially a thermoplastic, and which is supplied to the gap between the pressure tool and a molding tool as a strip with a width which corresponds to that of the adhesive closing part which is to be produced. The pressure tool is a pressure roller 3. The molding tool is a mold roller designated as 5 in its entirety. The two rollers are driven in the directions of rotation given in FIG. 1 by curved arrows 7 and 9 so that between them a conveyor gap is formed through which the plastic strip is conveyed in the transport direction, while at the same time in the gap as the shaping zone the plastic strip is molded into the backing 10 of the adhesive closing part and the backing 10 acquires the shape necessary for forming the interlocking means on the side adjacent to the mold roller 5 by the shaping elements of the mold roller 5.

[0020] For this purpose, the mold roller 5 on the periphery has a screen 11 with individual mold cavities 12. One such mold cavity 12 is shown enlarged by way of example in FIG. 2. Furthermore, the mold cavities 12, as is not detailed, are regularly distributed over the mold roller 5 with its screen 11 on the outer peripheral side, and the distribution and number can be freely selected. FIG. 2 shows a lengthwise section of the mold cavity 12 used at the time, the boundary walls 13 which are opposite in the lengthwise section being continuously provided with a convex path 14. It goes without saying that the two indicated boundary walls 13 with respect to the rotationally-symmetrical structure of the mold cavity 12 are fundamentally part of the terminating shaping wall 15 which is bordered by the screen material 11 of the mold roller 5. With these mold cavities 12 it is possible to produce interlocking means in the form of a stem part 17 which is provided with a head part 16.

[0021] As FIG. 2 furthermore shows, the curvature of the respective path 14 in the direction of the head part 16 to be molded is made more pronounced than in the direction of the base part 18 via which the stem part 17 is connected to the backing 10. It has been found to be especially advantageous here if, viewed from the lengthwise direction of the stem part 17 in the direction of the head part 16, the path 14 with its more pronounced curvature begins above the middle, preferably in the upper third.

[0022] To obtain the indicated cavities 12 with their rotationally symmetrical structure in the form of a hyperboloid, galvanic coating processes have proven effective, in which first a cylindrical cavity (not shown) is coated with a coating material until the convex path 14 results. Furthermore, optionally the convex path 14 can also be produced by way of a laser process from a solid screen or grating material.

[0023] The interlocking means shown in FIG. 3 can be obtained with the above described process. The symmetrical structure is formed directly by production in a mold cavity 12 as shown in FIG. 2. The interlocking means in question can have a geometrically very small structure, for example can have a height of only 0.4 mm, with a width of the closure head of roughly 0.6 mm. In this embodiment the cross section of the stem part 17 is roughly 0.25 mm. Furthermore, as shown in FIG. 4 a plurality of these interlocking means can be located on the backing 10. The head shape of the head part 16 need not be further reworked; however it can be provided in certain processes that the heads of the interlocking means be subjected to a calender process or the like and in doing so be calendered. Furthermore, it can be possible to make cuts in the outside contour of the closed, annular head part 16 in order to obtain in this way a plurality of interlockings along the head part 16. The interlocking means shown in FIGS. 3 and 4 can also have a different appearance, especially regarding their head part 16, for example they can be provided with head geometries as have already been shown in PCT/WO 00/00053. If there is the danger that the edge-side free ends of the head parts 16 which are hexagonal in cross section in this case should be unintentionally turned up when being ejected from the screen roller 11, the head parts 16 can be re-calendered from the top by way of a calender roller so that they then assume the shape as shown in FIG. 3 on the condition that the middle area 20 of the respective head part 16, which area which is arched upward convexly, arches inward concavely (not shown) in the direction of the stem part 17. The middle areas 20 which are shown in FIG. 4 from the top and which are encompassed by the hexagonal edge shape of the head part 16 would therefore arch into the plane of the drawings when viewed in the direction of looking at FIG. 4 and in this way would form a depression, in contrast to FIG. 3.

[0024] Biologically decomposable materials (BAW) are also possible as the moldable materials for implementing the process as claimed in the invention, and the materials in question can also be produced based on renewable or petrochemical raw materials or combinations of the two. 

1. A process for producing an adhesive closing part with a plurality of interlocking means which have a symmetrical structure and which are connected integrally to a backing (10), in the form of a stem part (17) which is provided with a head part (16) and in which a moldable material is supplied to the shaping zone between a pressure tool (3) and a molding tool (5) and they are driven such that the backing (10) is formed in the shaping zone and conveyed in the transport direction, and in which mold cavities (12) with boundary walls (13) opposite one another are used as the shaping element on the molding tool (5), characterized in that, at least viewed in the lengthwise section of the respective mold cavity (12) the opposing boundary walls (13) are continuously provided with a convex path (14).
 2. The process as claimed in claim 1, wherein the curvature of the respective path (14) in the direction of the head part (16) which is to be molded is made more pronounced than in the direction of the base part (18) via which the stem part (17) is connected to the backing (10).
 3. The process as claimed in claim 2, wherein viewed from the lengthwise direction of the stem part (12) in the direction of the head part (16), the respective path (14) with its more pronounced curvature begins above the middle, preferably in the upper third.
 4. The process as claimed in one of claims 1 to 3, wherein some of the lengthwise sections with their convex paths run into the corners of the boundary walls (13) such that the cross section of the stem part (17) and/or of the head part (16) is formed as a polygon, especially a hexagon.
 5. The process as claimed in one of claims 1 to 4, wherein the respective mold cavity (12) is made as part of a mold screen (11) or mold grating of the molding tool (5).
 6. The process as claimed in claim 5, wherein each part of the interlocking means, preferably the head part (16) and the stem part (17), has its own mold screen (11) or mold grating with different cross sections.
 7. The process as claimed in claim 5 or 6, wherein the mold screen (11) or the mold grating is made as a jacket part which is placed around the shaping tool (5) in the form of a roll body and is joined to it.
 8. The process as claimed in one of claims 1 to 7, wherein the mold cavities (12) with their paths (14) are produced by way of a galvanic coating process or by using a laser.
 9. The process as claimed in one of claims 1 to 8, wherein the size of the mold cavities (12) is chosen such that the height and/or the width of the interlocking means is between 0.05 mm and 1 cm and wherein there are up to 500 interlocking means per cm² of the backing (10).
 10. The process as claimed in one of claims 1 to 9, wherein the mold cavities (12) and moreover the interlocking means are formed as rotationally symmetrical parts, especially in the form of hyperboloids. 